System of control for electric motors.



v T. E. BARNUM. SYSTEM OF CONTROL FOR ELECTRIC MOTORS.

' I APIILIUA'I'VION FILED, June, 1908. v

Patented May 2, 1911.

'4 SHEETS-SHEET 1.

T. B. BARNUM. SYSTEM OF CONTROL FOR BLEGTRIG MOTORS.

APPLICATION FILED JULY 6, 1908.

Patented May 2, 1911;

4 SHEETS-SHEET 2.

T. E. BARNUM. I SYSTEM OF CONTROL FOB. ELECTRIC MOTORS.

APPLICATION FILED JULY 6, 1908. I 991,189. PatentedMay 2,1911.

4 SHEETS-SHEET 3.

T. E. BARNUM. SYSTEM OF CONTROL FOR ELECTRIC MOTORS.

v APPLICATION FILED JULY 6, 1908. I

991 ,189. 1 Patented May 2, 1911.

4 SHEETS-SHEET 4.

' 7ZZ7Z65J057 W (A w MWMA 4 54; A. 7% aw UNITED STATES PATENT OFFICE.

THoMAs E. BARNUM, or MILWAUKEE, WISCONSIN, nssre'non. 'ro THE CUTLER.

HAMMER MFG. 00., or MILWAUKEE, WISCONSIN, A CORPORATION or WIS- CONSIN.

Application filed July 6, 1908. -Serial No; 442,203.

State of Wisconsin, have invented new and useful Improvements in Systemsof Control for Electric Motors, of which the following is a full, clear,concise, and exact description, reference being had to the accompany-.ingdrawing, forming a part of this specification.

My invention relates to improvements in systems of control for electricmotors, and more particularly to-systems for controlling motor operatedvalves wherein an overload 7 device is employed.

One-objectof my'invention is to provide means for'renderlng the overloaddevice 1noperative for atemporary period after the motor circuit isclosed. .A further object is to provide means for indicating when'themotor circuit is closed,

A further object is top'rovidemeans for indicating when the motor hasattained nor mal speed. i

A further object of my invention is to provide means for indicating thedirection in which the 'motor was last operated.

A further object is to prevent the motor from operating in the samedirection twice in succession.

Further objects and advantages of my invention will be hereinafter setforth.

In order to more. clearly disclose my invention; I have illustratedcertain embodiments thereof in the accompanying drawings.

' In'the accompanying drawings-Figure 1 diagrammatically illustrates asystem em-- bodying my invention; Fig. 2 diagrammaticallyillustrates asystem similar to that shown in Fig. 1 with certain additional featheinterlock shown in Fig. 1.

tures. Figs. 3, 4 and '5 diagrammatically illustrate other featureswhich may be embodied in the system shown in Figs. 1 and 2. and Fig. 6illustrates a modified form of In the embodiment of my invention,illustrated in Fig. 1, I have shown a motor hav-' ingan armature a, andafield winding Themotor is supplied with current from f the main lines 1and 2 through a reversing switch BS. The reversing switch RS is providedwith two electromagnetic windings specificatio n of Letters Patent.

- SYSTEM'OF CO NTROL FOR ELECTRIC MOTORS.

Patented B and C. The winding B is provided with a plunger 6 and'thewindingvC is provided with aplunger c. Mounted on the plunger b andinsulated therefrom are two switches Mounted on the plunger 0 andinsulated therefrom are switches 0 and 0 also prefer-.

iably in the 'form of disks. The disk 0 is adapted to-bridge stationarycontacts 7 and 8, and the switchc is adapted to bridge stationarycontacts 9 and 10. At its upper end 5 carries a contact plate, or switchadapted to bridge stationary contacts 11 and 12. Plunger c carries atits upper end a contact plate, or switch 0 -adapted to bridge stationarycontacts 13 and 14. To prevent both of these plungers from being raisedat the same time I provide an interlocking device comprising a bar Dpivoted at its center. This bar D is adapted to be engaged at itsopposite end by pins b and 0", carried by theplungers b and 0,respectively. For controlling the'circuit through winding B, I provide apush button Band for controlling the ci cuit through winding C I providea push utton C.

An overload wi nding G is connected in the motor circuit and is providedwith a plunger 9, carrying a contact 9, which normally bridgesstationary contacts 17 and 18 connected in circuit with the windings Band C. Contacts 15 and 16 are connected in a short circuit around thewinding G and are adapted to be bridged by a switch 6 carried by theplunger e of a solenoid E which is connected across the terminals "ofthe arfield, winding 7". The other terminal of the field winding" f isconnected by conductor 23 with one terminal of the overload winding G,the other terminal of the windin B being connected to the main line 2.ontact 4 is connected by conductor-24 to contact 9, which is connectedby'conductor 25 a to one terminal of the armature a. The other terminalof the armature a is connected by conductor 26 to contact 6, which isconnected by conductor 27 to contact 7. The winding connected across thearmature a by conductors 28 and 29. The windings B and C are connectedin circuit in parallel. The circuit for winding B extends from main line1 by conductor 30 through push button B, conductors 31 and 32, throughthe winding B by conductor 33 to contact 17 across switch 9' to contact18 and thence to main line 2. The circuit for winding C extends fromconductor 30 through push button C, conductors 34 and 35, through thewinding C to conductor 33 and thence back to the main line 2, as alreadytraced. Contact 14 is connected to conductor 34:. Contact 13 isconnected by conductor .36 to contact 12. Contact 11 is connected toconductor 32. Conductor 37 connects conductor 36 with conductor 19.Conductor 38 connects contact 15 to conductor 23 on one side of thewindingv Cr and conductor 39 connects contact 16 to main line 2. v

The following is a description of the operation of this system: Assumingthat the several windings are deenergized and their plungers are in thepositions shown in the drawing, if push button B is closed,'current willflow from main line 1 byconductor 30 through push button B by conductors31 and 32 through the winding B by conductor 33 to" contact 17 acrossswitch g to contact 18, and thence to the main line 2. This 1 results inthe energization of the winding B which lifts its -plunger b, causingthe disks 6 and b to bridgethe contacts 3 and 4;, and 5 and 6respectively. This results in the closure of the motor circuit. I

The motor circuit may be traced from main line 1 by'conductor 19 tocontact 3, across disk b tocontact 4, by conductor 24 to contact 9,thence by conductor 25 through the armature a by conductor 26 to contact6, across disk 6 to contact 5, by conductor 22 through the series fieldwinding 7 by conductors 23 and 38 to contact 15 across switch e tocontact 16 and thence by conductor 39 to main line 2. The motor is thusstarted, but owing to the short circuit around the overload windingB,through conductors 38 and 39, the overload device is at this timeprevented from operating to open the circuit of the winding B. At thesame time that the motor circuit is closed, contact plate 6 bridgescontacts 11 and 12 with the result that a maintaining circuit forthewinding B is established. This circuit may be traced from main line 1 byconductors 19 and 37 to contact 12 across contact plate I)? to contact11, thence by conductor 32 through the winding B to conductor 33 and tothe main line '2, as already traced. As soon as this maintaining circuitis established the push button B may be released with out interruptingthe circuit through the winding B.

As previously stated, when the motor circuit is first closed theoverload device G is prevented from operating, owing to the fact that ashort circuit around the same is established by switch e bridgingcontacts 15 and 16. Inasmuch as there is little or no drop in potentialacross the armature when the motor circuit is initially closed there islittle or no drop in potential across the terminals of the winding E,and hence the same will not respond. However, as the armature speeds upit generates a counter electrometive force which increasesproportionally to the increase in the armature speed, and causes agradually increasing drop in potential across the armature. The increaseof the drop in potential across the armature causes a correspondingincrease of the potential at the terminals of the winding E. When themotor reaches normal speed the potential at the terminals of the windingE is sufiiciently increased to cause the same to respond and raise itsplunger, thus raising the contact plate e from the contacts 15 and 16.This results in opening the short circuit around the overload winding Gand in consequence the winding G is connected in serieswithwthemotor. Ifnow an excessive current fiowsthrough the motor, the Winding Gr will beenergized and raise its plunger, thus opening the switch 9'. Thisresults in the opening of the circuit of the winding B which permits itsplunger 6 to fall, thus opening the motor circuit.

The system shown and described is particularly applicable forcontrolling motors for operating valves. In such services the motorbecomes stalled upon the valve reaching either its final, open, orclosed position. When the motor becomes stalled an excessive flow ofcurrent through the motor is caused, which energizes the overloadwinding G, which in turn opens the circuit through the reversing switch,with the result already described. It should be understood, however,that this system is applicable to other service, and as will hereinafterbe explained, means may be provided for opening the motor circuit atwill. It should also be understood that although I have not shown astarting resistance for protecting the motor during the starting period,such resistance may be employed without departing from the spirit'of myinvention.

As already explained, as soon as the overload device operates, it causesthe deenergi- Zation of the winding B which, results in the falling ofthe plunger 6, thus opening the motor circuit. As soon as the motorcircuit is opened the overload winding G is deener gized and its plunger9 falls, causing th contact plate g to again bridgethe contacts 17 and18. Also, as soon as the motor comes to a state of rest the winding E isdeenergized and its plunger 6 falls, causing the contact plate e tobridge the contacts 15 and 16. If new it is desired to cause the motorto run in an opposite direction, the push button C is operated, whichcloses the circuit of the winding C. This circuit may be traced from themain line 1 by conductor 30 through push button C. by conductors '34 andthrough winding C to conductor 33 and thence back to the opposite sideof the main line, as already traced. When the winding C becomesenergized it raises its plunger 0, which closes the motor circuit. Themotor circuit may now be traced from main line 1 by conductor 19 tocontact 3, by conductor 20 to contact 8 across the disk 0' to contact 7,by conductor 27 to contact 6 by conductor 26 through the armature a toconductor 25, contact 9, thence-across disk 0 to contact 10 by conductor21 to contact 5,

theme by conductor 22 through the series field winding f by conductors23 and 38 to contact 15 across switch 6 to contact 16 and then byconductor 39 to mainline 2. It will thus be seen that the motor iscaused to operate in the opposite direction from that already described,and that the shortcircuit around the overload windingG is againestablished, preventing the same from responding. When the plunger C israised it causes contact plate 0 to bridge contacts 13 and 14', whichestablishes a maintaining circuit for the winding C, which may be tracedfrom the main line 1 by conductors 19 and 37 to contact 13 across switch0 to contact 14 by conductor 35 through the winding C,

to conductor 33, and thence to the opposite side of the main line. Thepush but-tion C can now be released without interrupting the circuit ofthe winding C. The operation from this point on is substantially-thesame as that alreadydescribed. When the motor attains normal speed thepotential at the terminals of the winding E is sufiicient to cause thesame to respond and raiseits plunger to open the short circuit aroundthe winding G. The winding G is thus placed in circuit in series withthe motorand upon an-excessive current flowing through the motor thewinding G is energized and raises.

the switch (1' which opens the circuit through the winding C. As soon asthe circult through the wmdmg C is opened 1ts plunger 0' falls, thusopening the motor circuit. The opening of the motor circuit causes thedeenerglzat on of the wmdlngs E and G, and .their plungers, therefore,fall to the position shown in the drawing. The motor may again bestarted and caused to operate in either direction, according to whichone of the push buttons is operated.

,The system shown in Fig. 2 is substantially the same as that shown inFig. 1, ex-

cept that instead of connecting conductor 36 to conductor 19 byconductor 37, I connect conductor 36 to conductor 30 by conductor 40,through lamp 41, push button 42 and conductor 43. The push button 42, inthis instance, is normally closed. The remainder of the circuitarrangement is precisely like that shown in Fig. 1. The operation ofthis system is also the same as that already described, with theexception that the maintaining circuit for the windings B and C extendsfrom conductor 30 by conductor 43 through push button 42, conductor 40through lamp 41, thence through either the windings B or C, according towhich one is energized, to the opposite side of the main line, asalready described. With this arrangement when either of the plungers bor c is operated, said maintaining circuit is closed, thus closing thecircuit through the lamp 41 which serves, when lighted, to indicate thatthe motor circuit is closed. If, after the motor has attained normalspeed and the short circuit hasbeen removed from around the overloadwinding G, an excessive current flows through the motor, the overloaddevice will operate to open the circuit through the winding G or thewinding B, according to which one has been energized. This results inthe falling of its plunger which opens the maintaining circuit andconsequently the lamp 41 ceases to burn,

which indicates that the motor circuit has been opened. The purpose ofthe push button 42 is to provide means whereby the motor may be stoppedat the will of the operator. As already set forth, when the maintainingcircuit isestablished the push button which was operated to initiallyclose the circuit through the winding energized, may be released. If newthe push button 41 is operated it will open said maintaining circuit,which will cause the deenergization of the reversing switch, which willresult in the opening of the motor circuit.

- As shown in Fig. 3 the maintaining circuit just described inconnection with Fig. 2 may be interrupted at contacts 44 and 45, saidcontacts being adapted to be bridged by the contact plate 6' when theplunger 6 is raised. With this arrangement the maintaining circuit willnot be closed until one of the plungers b or 0 has been raised and untilthe winding E has been energized to raise plunger 0 to cause the contactplate e, carried thereby, to bridge the contacts 44 and 45. As thewinding E will not raise its plunger until the motor has attained anormal speed, circuit will not be closed through the lamp until themotor has attained full speed. With this arrangement it is necessary tomaintain one of the push buttons B or C closed until the motor hasattained full speed.

In Fig. 4 I have shown, in addition to the maintaining circuit, shown inFig. 2, a

to contact 48, across contact plate e, when raised, to contact 49 andthence by conductor 50 to conductor 33. With this arrangement, as soonas the reversing switch has been operated, causing either of theplungers b or c to be raised, circuit will be closed through lamp 41, asdescribed in connection vwith Fig. 2. l/Vhen the motor attains fullspeed and the winding E raises its plunger, contact plate 6 will bridgecontacts 49 and 48, with the result that circuit will be also closedthrough lamp 46. It will thus be seen that lamp 41 indicates when themotor circuit is closed while the lamp 46 indicates when the motor hasattained full speed.

In Fig. 5 the circuit arrangement shown is like that shown in Fig. 1.But in this instance conductor 34 is provided with a winding '51 andconductor 31 with a winding 52. These windings are preferably inalinement and are provided with'a common plunger 53. ,54 is anindicating arm pivoted at 55 and having its lower extremity connected toplunger 53. With this arrangement, when the circuit is closed throughthe reversing switch by the closure of push but-- ton B, the winding 52will be energized, exerting a pull on plunger 53, which throws theindicator arm 54 to the left, as shown in the drawing. The indicatingarm will remain in this position until the push button C is operated tocause the motor to run in the opposite direction. Upon the closure ofthe push button C the winding 51 will be energized, attracting plunger53, which will throw the indicating arm to the right. It will thus beseen that this indicating arm serves to indicate the direction-in whichthe motor was last operated. When this system is applied to a motor foroperating a valve,

thisarm will serve to indicate whether the valve is open or closed. V

Fig. 6 shows an interlocking arrangement forpreventing the energi'zationof either of the windings B or C of the reversing switch twice insuccession. This interlock comprises a bar 60 pivoted at its center andhav-.

ing its extremities projecting into the paths of the projections 79 and0 carried by'the plungers b and a respectively. The right hand extremityof the bar 60 carries contact brushes 61 and 62. The brush 61 engageswith a contact segment 63, while the brush 62 is adapted to engage witheither of the segments 64 or 65 The left-hand extremity of the bar 60carries brushes .66 and 67. The brush 66 engages with the contactsegment 88, while the brush 67 is adapted to engage either of thecontact segments 69 or 70. The brushes 61 and 62 are insulated from thebrushes 66 and 67.

5 lines.

.the push button C.

ceases The circuit connections are as follows: Winding B is connected tocontact 12, and contact 12 is connected to segment 68. Winding C isconnected to contact 13, and contact 13 is connected to segmentf63.Contact segment 65 is connected by conductor 71 through push button C toconductor 30. Contact segment 69 is connected by conductor 72 throughpush button B to conductor 30. Contact 11 is connected by conductors 73and 74 through push button 75 to conductor 30. Contact button 14 isconnected by conductor 76 to conductor 74. Contact segments and 64 aredead.

Assuming that the bar 60 is in the position shown in the drawing,circuit may be closed through winding B by closing push button B. Thiscircuit may be traced from conductor 30 through push button B byconductor 72 to segment 69 to brush 67 by bar 60 to brush ,66. thence tocontact segment 68 to contact-12 through winding B and thence to theopposite side of the main line, as already traced in connection with theother figures. Circuit through the winding B having been closed, plunger6 will be raised to close the motor circuit. At the same time the projection b will strike the left-hand extremity of the bar 60 and turn thesame on its pivot until it reaches the position shown in dotted In thisposition the brushes 66 and 67 would engage segments 68 and 70, whilethe brushes 61 and 62 would engage the segments 63 and 65. In thisposition the circuit through the winding by conductor 72 would be openand the winding B would be deencrgized but for the fact that the contactplate b bridges the contacts 11 and 12 and establishes a maintainingcircuit therefor. This maintaining circuit may be traced from conductor30 through push button by conductors 74 and 73 to contact 11 acrosscontact plate 72 to contact 12, thence through the winding B to theopposite side of the main line, as already traced. The motor ma bestopped at any time by-operating the pus turned to such position untilafter the winding C has been energized. However, the winding C may beenergized by operating The circuit for the winding for-C may then betraced from conductor 30 through push button C by conductor 71 tosegment 65 and brush 62 to brush 61 and segnient 63 to contact 13,thence through the winding C to the opposite side of the line. Thisresults in the raising of the plunger 0 which closes the motor circuitto cause the motor to run in an opposite di-' rection. .When the plunger0 is raised it returns the bar 60 to position shown in full lines and atthe same time causes the contact 'plate 0 to bridge the contacts 13 and14,

which establishes a maintaining circuit for.

I claim as new and desire to secure by Let-v ters Patent, is:

1. In a system of control for electric motors, the combination with anoverload device, of means rendering said overload device inoperativeupon closure of the motor circuit and automatically rendering the samefree to respond after a predetermined period.

2. In a system of control for electric motors, 'the combination with anoverload de-' vice, of electromagnetically controlled means forrendering said overload device inoperative for a temporary period afterthe motor circuit is closed.

3. In a-system of control for electric motors, the combination with anoverload device, means tending to render said overload deviceinoperative, and automatic means for operating said former means torender said overload device free to operate when the mo- 7 tor circuitattains a predetermined speed. I

4. In a system of control for electric motors, the combination with anoverload device, means tending to render said overload deviceinoperative, and an. operating windmg for said means adapted to beconnected across the motor armature, said winding being adapted toactuate said means to render said overload device free to operate whenthe motor has attained a predetermined speed.

5. In a system of control for electric motors, the combination with anelectromagnetic overload device, of a switch tendingto establish a shortcircuit around the operating winding of said overload device, and meansfor automatically operating said switch to open said short circuit whenthe motor has attained a predetermined speed.

6. In a system of control for electric motors, the combination with anelectromagnetic overload device, of a switch tending to short circuitsaid overload device, and an operating winding for said switch, adaptedto be connected across the motor armature, said winding being adapted toactuate said switch to open said short circuit when the motor hasattained a predetermined speed.

7. In a system of control for electric motors, the combination withamain switch, of

an electromagnetic winding for operating said switch, a switch forcontrolling the circuit of saidwinding, an overload device for causingthe denergization of said winding upon an excessive flow of currentthrough the motor, and automatically controlled means for rendering saidoverload device inoperative for a temporary perlod aftersaid main switchis closed.

8. In a system of control for electric motors, the combination with amain switch for controlling the motor circuit, an electro; magneticwinding for operating said main switch, a switch for'controlling thecircuit of said windingand tending to stand in an-v open position, meansoperated upon the closure of said main switch for establishing amaintalnlng c1rcu1t for sald wlndmg, an

overload switch connected in said maintaming-circuit and adapted to beopened upon an excessise flow of Vurrent through the motor circuit, andautomatically con trolled means for preventing the operation of saidoverload switch for a temporary period after the closure of said mainswitch.

'9. In a system of control for electric motors, the combination with amain switch, of an electromagnetic winding for operating said switch, aswitch for controlling the circuit of said winding, an overload devicefor causing the deenergization of said winding uponan excessive flow ofcurrent through the motor, a switch tending to short circuit .theoperating winding of said overload device, an operating winding for saidlast mentioned switch adapted to be connected across the motor armaturefor actuating said switch to open said short circuit when the' motor hasattained a predetermined speed.

10. Ina system of control for electric motors, the combination with amain switch for controlling the motor circuit, anioperating windingtherefor, a switch forcontrolling the circuit of said winding andtending to stand in open position, means operated upon the closure ofsald main switch for establ1sh1ng a-maintalning clrcult for saidwinding, a switch connected in said maintaining of said overload device,and an operating winding for 'said last mentioned switch adapted tobeconnected across the motor armature for actuatlng said switch to opensaid' short circuit when the motor has attained a predetermined speed.

11. In a system of control for electric m0- tors,- the combination witha pair of switches adapted to cause themotor to operate in oppositedirections, ah overload device for causing either of said switches, whenclosed,

to open upon an excessive flow of current through the motor circuit, andautomatically controlled means for rendering said overload deviceinoperative for a predetermined period after the motor circuit isclosed.

12. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in oppositedirections, means for preventing the closure of both of said switches atthe same time, an overload device for causing either of said switches,when closed, to open upon an excessive flow of current through themotor, and automatically controlled means for rendering said overloaddevice inoperative for a temporary period after the motor circuit isclosed.

13. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in oppositedirections, means necessitating the closure of said switchesalternately, an overload device for causing either of said switches,when closed, to open upon an eX- cessive flow of current through themotor, and automatically controlled means for rendering said overloaddevice inoperative for a temporary period after the motor circuit isclosed.

14. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in oppositedirections, an operating winding for each of said switches, means forcon trolling the circuits of said windings, means for necessitating theenergization of said windings alternately, an overload device foropening the circuit of either of said windings, when energized, upon anexcessive flow of current through the motor, and automaticallycontrolled means for rendering said overload device inoperative foratemporary period after the motor circuit is closed.

15. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in oppositedirections, an operating windin for each of said switches, means forcontro ling the circuits of said windings, an overload device foropening the circuit of either of said windings, when energized, upon anexcessive flow of current through the motor, a switch tending to shortcircuitlthe operating winding of said overload device, and automaticmeans for operating said switch to open said short-circuit when themotor has attained a predetermined speed.

16. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in opposite,directions, an operating'winding for each of said switches, meansoperated upon the closure of each of said switches for establishing amaintaining circuit for its operating winding, an overload device foropening the circuit of either of said windings, when energized, upon anexcessive flow of current through .the motor, a switch tending toshort-circuit the operating winding of said overload device and anoperating winding for said last mentioned switch adapted to be connectedacross the motor armature for actuating said switch to open saidshort-circuit when the motor has attained a predetermined speed.

17. The combination with a pair of independently movable switchestending to stand in open position, of means necessitating closure ofsaid switches alternately.

18. The combination with a pair of switches tending to stand in openposition, of an operating winding for each of said switches and meansnecessitating the energization of said windings alternately.

19. The combination with a pair of electromagnetically operated switchestending to stand in open position, of an electrical interlocknecessitating the closure of said switches alternately. 20. Thecombination with a air of switches, of an operating winding 'or each ofsaid switches, and a switch operated upon the closure of each of saidfirst mentioned switches necessitating the energization of saidoperating windings alternately.

21. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in oppositedirections, an operating winding for each of said switches, means forcontrolling the circuits of said windings from a distance andmeansnecessitating the energization of said windings alternately.

22. In a system of control for electric motors, the combination with apair of switches adapted to cause the motor to operate in oppositedirections, an operating winding for each of said switches, means forcontrolling the circuits of said windings from a distance, meansoperated upon the closure of each of said switches for establishing amaintainin circuit for the operating winding thereof and means operatedupon the closure of each of said switches for opening the initialcircuit of the winding thereof, said last mentioned means necessitatingthe energization of said windings alternately.

23. In a system of control for electric motors, the combination, with anoverload de vice, of automatically controlled means for rendering saidoverload device inoperative for a temporary period after the motorcircuit is closed, and automatic means for indicating when the overloaddevice is free to operate.

24. In a system of control for electric motors, in combination anoverload device,

means for short circuiting the operating winding of said overload devicefor a temporary period after the motor circuit is of said switch forestablishing a maintaining.

circuit for said winding and an electroresponsive indicatmg deviceconnected 1n said mamtammg circult.

26. In a system of control for electric motors, the combination with apair of switches for causing the motor to operate in oppositedirections, means for controlling the operation of said switches from adistance, and automatic means for indicating which of said switches waslast operated.

27. In a system of control for electric motors, the combination with apair of switches for causing the motor to operate in oppositedirections, an operating winding for each of said switches, means forcontrolling the circuits of said windings from a distance and anindicating device adapted to be automatically moved to one position whenone 9f said windings is energized and into another position when theother of said windings is energized.

28. In a system ofcontrol for electric motors, the combination with apair of switches for causing the motor to operate in oppositedirections, of an operating winding foreach of said switches, means'forcontrolling the circuits-of said windings from a distance, an indicatingdevice and a pair of o eratin windin s for moviiw said in-' clicatingdev ice in opposite directions, one of said windings being connected inseries with each of the operating windings of said switches. v

29. In a system of control for electric motors, the combination with amain switch, of means for controlling the operation of said switch froma distance, means for indicating when said main switch is closed, an

overload device for causing said main switch to open upon an excessiveflow of current through the motor, and automatic means for renderingsaid overload device in operative for a temporary period after the motorcircuit is closed.

30. In a system of control for electric motors, the combination with amain switch,

of means for controlling the operation of said main switch from adistance, means for indicating when said switch is closed, an overloaddevice for causing said main switch to open upon an excessive How ofcurrent through the motor, automatic means for rendering said overloaddevice inoperative until the motor has attained a predetermined speed,and means for indicating when the motor has attained said predeterminedspeed.

31. In a system of control for electric motors, the combination with amain switch, of anoperating winding therefor, means for controlling thecircuit of said winding from a distance, means operated upon the closureof said switch for establishing a maintaining circuit for said winding,and an electro-responsive indicating device connected in saidmaintaining circuit, an overlgad device for causing the denergization ofsaid winding upon an excessive flow of current through the motor, meanstending to shortcircuit the operating winding of said overload device,said means being adapted to automatically open said short-circuit whenthe motor has attained a predetermined speed and means for indicatingwhen said short circuit has been opened.

32. In a system of control for electric motors, the combination with apair of switches for causing the motor to operate in oppositedirections, an operating winding for each of said switches, means forcontrolling the circuits of said windings from adistan'ce, an overloaddevice for opening the circuit through either of said windings, whenenergized, upon an excessive flow of currentthrough the motor,automatically controlled means for rendering said overload deviceinoperative for a predetermined period after the motor circuit isclosed, and an indicating device adapted to be automatically movedinto'one position upon the closure of one of said switches and intoanother position upon the closure of the other of said switches.

V 33. In a system of control for electric motors, in combination, a pairof switches for causing the motor to operate in oppo site directions, anoperating winding for each of said switches, means for controlling .thecircuits of said windings from a distance, means necessitating theenergization of said windings alternately, an overload device foropening the circuit of either of said windings, when energized, upon anexcessive flow of current throughthe motor, and automatically controlledmeans for rendering said overload device. inoperative for a temporaryperiod after the motor air-- cuit is closed.

In witness whereof, I have hereunto subscribed my name in the presenceof two witnesses. I i THOMAS E. BARNUM.

Witnesses OsoAR A. KELLER,

VVALTER E. SARGENT.

